This is a non-provisional application claiming priority to the Mexican Patent Application, Document Number NL/a/2004/000086, filed on Nov. 4, 2004.
1. Field of the Invention
Applicant's invention relates to the field of leak detection for underground pipes, and more specifically to a method for locating leaks in underground nonmetallic pipes through detection of electric field frequencies within the underground nonmetallic pipes.
2. Background Information
Pipe systems have historically been placed underground to conduct a variety of substances to and from various locations. The pipes that make up these pipe systems have typically been constructed from both metal and nonmetal materials. Inevitably, especially with nonmetallic pipes, breaks and cracks will form in the pipes over time, causing the substances they carry to leak into the surrounding ground and underground water, thereby often contaminating the soil, water, environment and ecosystem surrounding the pipes. These breaks and cracks occur as the pipes are no longer able to resist the forces exerted on them by the surrounding ground environment. The potential mess can be costly, and sometimes impossible to clean up. Furthermore the potential damage to the soil, water and surrounding environment or ecosystem can be irreversible. Thus, it is desirable to have a method for detecting and determining the location of leaks in nonmetallic pipes caused by breaks or cracks in the pipes. The present invention provides a system and method for locating leaks in nonmetallic pipes quickly and efficiently, thereby reducing or even eliminating the potential costly clean up and damage to the environment.
There exists in the prior art several related patents. U.S. Pat. No. 3,776,032 discloses protection of an inflow of either gas or liquid into a well. The detection occurs during the drilling of the well for the prevention of blowouts. The detection process involves the use of pressure mud pulses from a pair of acoustical transducers, which generate signals in the form of pressure waves, both before the drilling mud is circulated to the drill bit and after drilling mud is circulated through the drill bit. The difference, if any, in the two signals are then converted to a signal then transmitted to the surface.
U.S. Pat. No. 4,114,721 discloses a pair of acoustic detectors moving through a well to detect sound which is indicative of a through casing leak, i.e., a leak that goes through the casing. The acoustic noise generated by the noise sources is monitored at two spaced-apart locations within the borehole. The signals, representing the monitored acoustic noise at each location, are transmitted uphole.
U.S. Pat. No. 4,101,827 discloses the detection of leaks in an underground pipe which is made of electrically insulating material, i.e., material that does not conduct electricity. The detection process involves partially filling the pipe with an electrically conductive fluid, such as tap water, passing an electrical current through the fluid to establish a voltage gradient along the length of the fluid in the pipe, and then analyzing the gradient to determine the location of the leak. The voltage source is electronically connected to one electrode which is immersed in the liquid at one pipe end, and to a second electrode which is driven into the ground. The method disclosed in this patent involves inserting a wire inside the underground pipe in order to properly determine the potential drop and the determination of the location of the leak or leaks is done by measuring the length of wire inserted into the underground pipe at the point where there is a potential drop, i.e., the point of minimal voltage.
U.S. Pat. No. 5,548,530 discloses a non-intrusive high-precision ultra-sonic leak detector system for pipelines for identification of the development of even very minute, i.e., millimeter size, leaks and locates them within several meters of their actual location in a segment between two site stations of the overall leak detection. Leaks are located and their locations determined by their effect on the pressure of the pipeline, and the effect of the pressure change on liquid density.
U.S. Pat. No. 6,442,999 discloses the same technology that is disclosed in U.S. Pat. No. 5,548,530 regarding detection of leaks in an underground pipeline system. However, U.S. Pat. No. 6,442,999 adds a master station to which site stations transmit sonic wave data in order to perform calculations to determine the presence of a leak and also their location.
U.S. Pat. No. 6,530,263 discloses a system for finding and locating leaks in a pipeline using loggers positioned along the pipeline at spaced intervals. These loggers detect and store sound data produced within the pipeline and download the stored sound data to a computer system to determine the location of the leaks.
U.S. Pat. No. 6,595,038 discloses an apparatus for determining the position of a leak in an underground pipe for fluid or gas using two acoustic sensors. The first sensor is coupled to the pipe while the second sensor is movable above the pipe. Both sensors detect sound either carried along the walls of the pipe or along fluid in the pipe.
U.S. Pat. No. 6,668,619 discloses a method and apparatus for locating the source of a leak in a pipeline using match pattern filtering techniques. These match pattern filters discriminate against background noise and pressure disturbances generated by other non-leak sources. This method uses acoustic signals to determine whether a leak exists and where it is located.
Finally, U.S. Pat. No. 6,650,125 discloses locating leaks of conductive fluids, such as ionized water, from non-conductive structures, such as pipes, through the use of a charge generator employed to charge and discharge the conductive fluid, and a capacitive type detector that can detect the variable charge that is induced in the fluid. This detector is handheld and portable.
However, the current art does not disclose a system and method for locating leaks in nonmetallic pipes that does not require the insertion of a wire or device into the nonmetallic pipe itself. Furthermore, none of the references disclose a system and method for locating leaks without intrusion into the nonmetallic pipe that is simple, inexpensive and accurate. Therefore, a need exists for a cost-efficient system and method for locating leaks in nonmetallic pipes without requiring intrusion into the pipes.